Sewing machine belt feeder with tensioner

A workpiece transporter for a sewing machine comprises an endless conveyor belt looped around a driving sheave and several deflecting rollers, the latter including a first and a second roller carried on the free ends of respective spring-loaded levers placing that belt only under a moderate tension. The first deflecting roller is closely juxtaposed with the upstream side of the driving sheave, its axis defining with that of the sheave and with the fulcrum of its lever an obtuse triangle whose vertex angle increases as that roller approaches the sheave when an obstacle retards the belt motion, such approach clamping the belt more tightly between the roller and the sheave for firmer entrainment.